Is surgical axillary staging necessary in women with T1 breast cancer who are treated with breast-conserving therapy?

BACKGROUND: In the post-Z0011 trial era, the need to perform surgical axillary staging for early-stage breast cancer patients, who are treated with breast-conserving therapy (BCT), is being questioned. We conducted a retrospective cohort study using the Surveillance, Epidemiology, and End Results (SEER) database to evaluate the safety of waiving surgical axillary staging in patients with T1 breast cancer treated with BCT. METHODS: A total of 166,615 eligible patients diagnosed between 2000 and 2012 were divided into staging (sentinel lymph node biopsy or axillary lymph node dissection) and non-staging (no lymph node examined or only needle aspiration biopsy of lymph nodes) groups. Propensity score matching (PSM) was performed to balance disparities between the two groups. Multivariate analysis with the Cox proportional hazards model was used to assess factors related to breast cancer-specific survival (BCSS). RESULTS: Although the tumor size at time of presentation was decreasing over years, the rate of surgical axillary staging increased from 93.3% to 96.9%. The 5-year BCSS rates of the whole cohort (before PSM) and matched cohort (after PSM) were 98.0% and 97.5%. Within the matched cohort, the BCSS was significantly longer in the staging group than in the non-staging group (P < 0.001). However, surgical axillary staging did not benefit patients who were 50–79 years old, had tumor size < 1 cm, histological grade I disease, or favorable histological types (tubular/mucinous/papillary) in stratified analyses (P > 0.05). Race, marital status, hormone receptors, and chemotherapy were not associated with the favorable impact of surgical axillary staging on BCSS (P > 0.05). CONCLUSION: Although surgical axillary staging remains important for T1 breast cancer patients treated with BCT, it might be unnecessary for patients with old age, small tumor, grade I disease, or favorable histological types. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s40880-019-0371-y) contains supplementary material, which is available to authorized users.